Transparent conducting oxide (TCO) coatings may be applied to substrates or over-coated on top of other previously deposited layers. Such layers may exhibit high transparency with electrical conductivity ranging from semiconducting to highly conducting. Accordingly, these coatings, or “thin films” as they are often referred to, may be used for a wide range of opto-electronic applications. For example, thin films may be used in the manufacture of electronic devices, such as, liquid crystal displays (LCDs), and touch panel devices (e.g., personal digital assistants (PDAs) and electronic controllers), photovoltaic solar cells and transparent thin film transistors to name only a few examples.
Known deposition techniques may be implemented during the manufacture process to deposit a metal oxide as the thin film on a substrate. Indium Tin Oxide (also commonly referred to as ITO) is often used because it can be deposited at low temperatures, results in smooth films, can be readily etched, and exhibits thermal stability. However, other amorphous or polycrystalline metal oxides may also be used depending on the desired properties of the thin film, cost, operational parameters, and other factors. Furthermore, vacuum deposition using sputtering is a large area process that is widely used in the coating industry.
Achieving the desired opto-electronic properties of the thin film is typically dependent on the amount of oxygen introduced during the deposition process. Unfortunately, controlling the amount of oxygen (or its partial pressure) can be very difficult, especially in large-area production sputtering systems. For example, the amount of oxygen from the target changes with target use. Oxygen from the substrate and internal surfaces of the vacuum chamber is subject to seasonal/daily humidity variations. Maintenance activities also alter outgassing of internal surfaces. In addition, there can also be air leaks in the system. Accordingly, optimizing TCO film properties by controlling the oxygen partial pressure is a delicate process, and ensuring film reproducibility is time consuming and expensive.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.